Technologies has been researched and developed for producing synthesis gas containing carbon monoxide and hydrogen from light hydrocarbons (e.g., natural gases) as a feedstock and then synthesizing fuel oil (e.g., kerosene, light oil, methanol) from the synthesis gas as a feedstock (such technique is referred to as the GTL technology).
For this purpose, the catalytic partial oxidation method (CPO) is known as one method for producing synthesis gas from light hydrocarbons.
This catalytic partial oxidation method is a method for producing synthesis gas. In this method, oxygen is added to source gas, such as natural gas containing light hydrocarbons (e.g., methane), which is fed to a reactor. The light hydrocarbons (e.g., methane, ethane) are converted to carbon monoxide and hydrogen by the action of a catalyst, such as nickel, ruthenium, rhodium, platinum, provided within the reactor (see the chemical equation described below).CmHn+m/2O2=mCO+n/2H2 
However, source gases, such as natural gases, often contain about between 5% and 20% of hydrocarbons of carbon numbers of 2 or higher (e.g., ethane, propane, butane, other than methane). Since such hydrocarbons of carbon numbers of 2 or higher have lower ignition temperatures than that of methane, they are liable to combust when mixed with oxygen and to be catalytically oxidized. As a result, there is a high possibility that such gases self combust in an oxygen mixer or a preheater that is located in the upstream of the catalyst layer of the catalytic partial oxidation reactor, which may present a great obstacle in terms of safety in designing apparatuses.
Furthermore, as for hydrocarbons of carbon numbers of 2 or higher, each hydrocarbon has a different ignition temperature and a different combustion concentration range. Therefore, the self combustion temperature of source gas varies depending on the ratio among hydrocarbons of carbon numbers of 2 or higher in the source gas, which makes the reaction control difficult.
In order to address such disadvantages, International Patent Publication No. WO98/49095 discloses the invention in which an injector having a plurality of mixing nozzles is attached to an inlet of a catalytic partial oxidation reactor so that hydrocarbon gas and oxygen gas are mixed under a high lineal speed condition where they do not self combust, and they are then fed to a catalyst layer of a partial oxidation reactor.
Patent Document 1: International Patent Publication No. WO98/49095